Generally, a vehicle is a machine that runs on roads by wheels powered by motor equipped on the vehicle, as to transfer persons or goods and to do various works, for example, including machines powered by motor such as internal combustion engine including gasoline engine and diesel engine, steam engine, electric motor (electric vehicle), gas turbine, or the like
As continuously developing with ever so new technology since introduced, in the noise related art field, the vehicle can be so silent that no sound could be heard by persons. Especially, the electric vehicle hardly generates any sound so that a person could hear no noise from the vehicle with his ears.
Here, the electric vehicle uses a direct current motor as its power and a storage battery as its electric source. The electric vehicle has many advantages such as no exhaust gas, or less noise. It has, however, shortcomings such as too large and too heavy battery, and too short running time.
However as the technology developing, recently a compact and light-weight battery developed, as a result the electric vehicle commercialized, even a hybrid car that uses both gasoline engine and electric motor introduced.
But, in cases of electric vehicles and hybrid vehicles, practically the noise of them is too low to be heard by pedestrians. This can cause sometimes car accidents between vehicles and pedestrians since a person walking could not hear or recognize that a car approaching to him.
National Highway Traffic Safety Administration (NHTSA) under DOT (Department of Transportation) in U.S.A had suggested Pedestrian Safety Enhancement Act of 2010 (PSEA) which includes least noise standard for hybrid or electric vehicles.
The standard applies hybrid or electric vehicles with least noise standards, because, not like internal combustion engines for which decreased noise is aimed, hybrid or electric vehicles generates so little noises rather that could cause accidents due to a person not hearing an near-approached car.
If proper noises are generated as a quiet car is moving, pedestrians could easily recognize that the car is approaching to him, and could avoid accidents such as minor collisions or fender-benders.
Safety should be preferred in traffic policies, the standard aims to much higher safety for vehicle drivers, bicycle drivers, pedestrians, or the like on roads in cities or expressways.
Usually, hybrid or electric vehicles, in lower speeds, did not operate gasoline or diesel engines resulting very quiet moving, and a person could not easily hear the approaching vehicles.
Therefore, hybrid or electric vehicles is required the least noise standard, when they is running at lower speeds such as below 18.6 miles/hour (30 km/h). This requirement considers that among various roads noises, traffic noises, and environmental background noises, the approaching vehicles should be heard by pedestrians.
Therefore, vehicle maker companies have needs to generate various noises according to the various vehicle models, in which noise select ranges are important. Properties of selected noises, however, should be corresponded to the noise requirements or standards, in addition that vehicles of same model should generate same group of noises or same noise.
To generate noises, as shown in FIG. 1, a speaker 5 equipped outside of a vehicle 1, in particular at area of a bonnet 2, may generate sound similar to engine noises of a vehicle.
The bonnet 2 on which the speaker S is installed, may have a double structure including inner space, as shown in FIG. 2, or a double structure including a support frame 2″ welded and joined to the body of the bonnet 2′ to form embossed structures, as shown in FIG. 3.
In case of the bonnet 2 of a double structure including inner space as shown in FIG. 2, a hole is formed on the inner bonnet at engine room side, and then the speaker S is screw tightened against timer face of the outer bonnet through the hole of the inner bonnet.
However, this structure, in which the speaker for vehicle is installed, has a critical problem that the screw fastening the speaker S onto the bonnet 2 is exposed to outside the bonnet 2, and decreases esthetic feelings for exterior of the vehicle.
In case of the bonnet 2 of a double structure including a support frame 2″ welded and joined to the body of the bonnet 2′ to form embossed structures, as shown in FIG. 3, the speaker S is not fastened directly onto the bonnet 2, rather the speaker S is fastened to a fastening member 3 which joined to the embossed structures of the support frame 2″.
Although this could solve the problem, that the exposed screw decreases esthetic feelings for exterior of the vehicle, still there is other problems that the sound or vibration from the speaker S should first transfer to the fastening member 3 before the bonnet 2. This problem may cause attenuation of the output of the sound or vibration being transferred.